The present invention relates to an ice thermal storage type air-conditioner in which ice is made or thawed by flowing a cooling medium in the interior of a heat transfer unit or units provided in an ice thermal storage tank, and an ice thermal storage tank used therein.
Ice making methods in ice thermal storage type air-conditioners include two kinds of static method and dynamic method. With the static method, icing forms and grows ice on a surface of a heat transfer unit or units provided in a thermal storage tank, so that there is caused a problem that heat transfer resistance increases with an increase in the thickness of ice and so ice making decreases in efficiency. With the dynamic method, a cooling medium of low temperature and low pressure is made to flow in the interior of a heat transfer unit or units provided on the bottom of an ice thermal storage tank to make ice, and then a cooling medium of high temperature and high pressure is made to flow to peel ice, which has grown, off the surface of the heat transfer unit so that ice pieces are permitted to come up to the upper portion of the thermal storage tank by their buoyancy and cold accumulates as ice in the thermal storage tank. An example of the dynamic method disclosed in Japanese Patent Laid-open Publication No. 42878/1996 is known.
In the prior art of the above publication, a solution is presented with respect to suppression of an increase in thermal resistance accompanied by the formation of ice and to enhancement of an ice filling rate for a volume of water in the tank. Since a plate evaporator is provided as the heat transfer unit on the bottom of the ice thermal storage tank, however, there is raised a problem that the ice filling rate for a container space in the ice thermal storage tank (the rate of occupation) decreases. Besides, because of peeling ice off the heat transfer unit, which will become an evaporator at certain periods in operation, there is raised a problem that the surrounding water is warmed.
It is an object of the present invention to provide an ice thermal storage type air-conditioner in which unused portions not contributing to ice making in an ice thermal storage tank are reduced to improve the ice filling rate of the ice thermal storage tank or to prevent a heat transfer unit from being damaged due to excessive icing, and an ice thermal storage tank used therein.